Stereo Integrated Amplifier (1981-82)
The power amplifier section of the Pioneer A-8 adopts a non-switching amplifier system which combines the merits of the class A amplifier’s high quality and the class B amplifier’s high efficiency for a continuous power output of 90 watts per channel, min at 8 ohms from 20 Hz to 20,000 Hz with no more than 0.005% total harmonic distortion.
The voltage amplification stage features two current detector circuits to control the bias circuit voltage and prevent the current flowing to the power transistors from being cut off.
As a result of these innovations, the distortion generated when the transistors are switched is suppressed, the dynamic distortion is improved and the sound takes on an extra dimension in clarity extended to the high-frequency range.
The power amplifier features a DC servo circuit employing an operational amplifier.
By adopting a DC servo circuit and incorporating an lET differential input circuit in the first stage, it has become possible to cut out the coupling capacitors, which cause colouration in the sound quality, and provide a direct coupled circuitry configuration from the AUX, TUNER and TAPE terminals through the outputs.
As a result, virtually distortion-free sound reproduction is ensured across a wide frequency spectrum from the ultra-low range to the ultra-high range.
This unit comes with a unique line straight switch which can be flipped to allow the signals to bypass the tone control circuit, balance volume and mode switch.
It is thus easy to provide a simple circuit configuration – something which is extremely important as far as the purity of the sound heard is concerned, MM/MC Equalizer With High S/N Ratio.
By using pictographs for the function position and speaker output display, operational ease is enhanced.
As soon as the A-8 protection circuit is actuated to protect the amplifier from damage when the speaker terminals have been short circuited in error or as soon as the muting circuit, which functions to prevent the unpleasant noise heard when the power is switched on and off, is made operational, the speaker output is cut off and indication is made by this red protection indicator lamp. The lamp changes over to green once the amplifier is operating normally again.
All the function switches and volume control which are used regularly are positioned on the right while all the sub-controls which are usually set up and then left without further adjustment are housed behind a movable panel at the left.
All the indicators that show the signal flow, output level and other modes of operation at a glance are housed on a panel in the center of the unit.
Power output: 90 watts per channel into 8Ω (stereo)
Frequency response: 5Hz to 100kHz
Total harmonic distortion: 0.005%
Damping factor: 60
Input sensitivity: 0.25mV (MC), 2.5mV (MM), 150mV (line)
Signal to noise ratio: 72dB (MC), 90dB (MM), 110dB (line)
Output: 150mV (line)
Speaker load impedance: 6Ω to 16Ω
Dimensions: 420 x 132 x 423mm